The present invention relates to gripper blocks and carrier blocks that are coupled to an apparatus that conveys tubing into a bore. For example, embodiments of the disclosed gripper blocks and carrier blocks are suitable for use with coiled tubing injection equipment for use in the oil and gas industry.
Coiled tubing has been used for many years to conduct various interventions within a bore, pipe, or pipeline, including drilling, completions, inspections, and other interventions. Coiled tubing apparatus includes a reel of tubing that is withdrawn or returned from the reel via an injector. The injector typically use a pair of opposed endless/infinite (i.e., looped) gripper chains mounted in a common plane. Coupled to the chains are a series of carrier blocks, to which are coupled replaceable gripper blocks. The opposing gripper blocks are configured to grasp the tubing and apply sufficient force to inject or retract the tubing from a bore as the gripper block/carrier block combination move in a loop via the gripper chains.
Various types of gripper blocks have been used over the years. One of the most common types includes a gripper block with a dovetail feature on its lower surface. The dovetail of the gripper block is configured to be slid into a complementary dovetail feature on an upper surface of the carrier block. This provides the ability to replace the gripper blocks relatively easily.
The dovetail connection, however, has several deficiencies. There needs to be sufficient clearance between the dovetail features of the gripper block and the complementary dovetail features of the carrier block to permit a user to slide the gripper block relative to the carrier block to couple/decouple the gripper block from the carrier block. This clearance, however, may permit movement of the gripper block relative to the carrier block during use.
This relative movement may have been tolerable with smaller tubing sizes. The industry, however, frequently is using larger diameter tubing (e.g., tubing greater than 2.625 inches/66.7 millimeter diameter) during operations than it has in the past. This larger diameter tubing imposes relatively greater forces on the gripper block and, consequently, the dovetail connection. Thus, the larger forces imposed by the larger diameter tubing may displace the gripper block from its aligned position relative to the carrier block and adjacent gripper blocks. This misaligned gripper block, then, could cause the misapplication or force and/or increased force to be applied to the tubing and/or the gripper block and/or the carrier block. Consequently, the misapplied and/or increased forces may risk binding the tubing and/or damaging the tubing, the gripper block, and the injector apparatus. For example, the narrow end portions of the dovetails act as a stress concentrator and pose a risk of breaking when the gripper block becomes misaligned relative to the carrier block.
Consequently, there is a need for an improved gripper block and carrier block assembly that provides easier assembly, tighter tolerances, and less relative movement between the gripper block and the carrier block during use. In addition, there is a need for an improved gripper block and carrier block that is capable of withstanding the larger forces encountered during use with larger diameter tubing.